This invention relates to a method and apparatus for controlling power steering.
Generally, the steering resistance of a motor car tends to increase as the car speed decreases so that when the steering resistance is cancelled by using a power steering device wherein oil is circulated by the operation of an oil pump, a satisfactory steering can be made with a small steering force even when the car speed is low. For this reason a power steering device has been used wherein the number of revolutions of the oil pump is increased when the car speed is low whereas as the car speed increases the number of revolutions of the oil pump is decreased, thereby enabling smooth steering. When the car speed increases to a predetermined speed above which power steering is not necessary the oil pump is stopped to save energy.
However on a downward path including many sharp curves, even when the car runs at a relatively high speed a large steering resistance is created. However, with the prior art power steering device utilizing a conventional control method and apparatus the oil pump stops when the car speed exceeds a predetermined value so that when the car runs down along a downward path including many sharp curves the power steering device would not operate thus requiring a large steering force. This difficulty can be obviated by increasing the car speed at which the oil pump stops, but with such measure, even when the car runs on a straight plane path the oil pump would stop thus consuming energy.